Ratio-measuring system



Nov. 23, 1948. D. w. MOORE, JR

RATIO-MEASURING SYSTEM Filed March 25, 1945 R. M S l J H 0 M m w m w .x m i m M. .m N w 1& 3 .8 1 c 0 Etiw M21. D a 0 3 W O 0 8 B w NN J 8 om mfizz zoz 2 A 8 J21 1523 202 2 now 8 8 8 L 22-12 65 r) 2 52:32 5:25 2 M52? @338 82:: d3 82;: 12 5553 J M250 J mmfi oi 8% Q: p 295328 p 822 m2 6 J c J 2 J 2 2 9 E Patented Nov. 23, 1948 RATIO -MEASURING SYSTEM David W. Moore, Jr., New York, N. Y., assignor to Fairchild Camera and Instrument Corporation, a corporation of Delaware Application March 23, 1945, Serial No. 584,465

7 Claims. 1

This invention relates to ratio-measuring systems and more particularly to systems for measuring the fuel-air ratio of the input to a combustion device, such as an internal combustion engine. 7

It is well known that, in the operation of combustion devices such as internal combustion englnes, it is highly desirable to maintain an accurately determined fuel-air ratio and that it is often desirable that such ratio be varied in a precisely predetermined manner over a given range of operating conditions of the engine. For example, in the case of an air-craft engine, it is desired to maintain the fuel-air ratio substantially constant under normal operating conditions but when maximum power is required, as during acceleration, it is desired to enrich the fuel-air mixture and conversely, when cruising over long distances, it is frequently desirable to reduce the fuel-air ratio to obtain maximum gasoline economy. In order to be able accurately to control the fuel-air ratio of a combustion device, it is desirable to have a continuous indication of the particular ratio obtaining at all times.-

It is an object of the invention therefore to provide a new and improved ratio-measuring system which is effective continuously to measure the ratio of two variable quantities, such as the ratio of the air-mass fiow and the fuel-mass flow, that is the fuel-air ratio of the input, to the com bustion device.

It is another object of the invention to provide a ratio-measuring system of the type described which is simple and economical in construction and reliable in operation.

In accordance with the invention, a system for continuously measuring the ratio of two variable quantities, such as the fuel-air ratio of the input to a combustion device, comprises means for developing a first electrical signal varying with a first of the quantities, for.example the air-mass flow, and means for developing a second electrical signal varying with the other of the quantities, for example the fuel-mass flow. The system also includes means for selecting an adjustable portion of one of the signals and means responsive to the difference between such portion of said one signal and the other of said signals for adjusting the selecting means to reduce the difference substantially to zero. The adjustment of the selecting means is then representative of the ratio of the two quantities, that is, of the fuel-air ratio of the input to the combustion device. By the term measuring, as-used herein and in the appended claims, is meant the derivation of an 2 effect representative of the ratio of the two variable quantities which may be utilized to give an indication or record of such ratio or to effect a control in accordance therewith.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings while its scope will be pointed out in the appended claims.

Referring now to the drawing, the single figure represents, partially schematically, a ratio-measuring system embodying the invention as applied to th measurement of the fuel-air ratio of the input to a combustion device, which may be an internal combustion engine.

Referring now to the drawing, there is represented, partially schematically, a system for continuously measuring the ratio of two variable quantities, such as the ratio of the fuel-mass flow to the air-mass fiow, that is the fuel-air ratio of the input, to a combustion device Ill, which may be an internal combustion engine. The system comprises an altemating-current supply circuit l l which may be connected to any suitable source, such as a commercial -cycle power line, and from which the several elements of the system'are energized. The system also includes means responsive to variations in a first of such quantities, for example the air-mass flow to the device I 0, for developing a first efiect varying with said quantity. This means may comprise an air-mass fiowmeter [2 connected in an air-intake conduit l3 to the combustion device i0 and a voltage-divider resistor l4 connected across or otherwise coupled to the circuit II and including an adjustable contact element Ha actuated by the airmass fiowmeter I 2 for developing an electrical signal varying with the air-mass flow to the device lll. If the air-mass fiowmeter I2 is of the power output type, it may be connected directly to actuate the adjustable contact Ha or, if it is not of the power output type, it may be coupled thereto, as shown, through a torque amplifier Hi. The air-mass fiowmeter i2 may be of any suitable type such as of the types described in applicant's copending applications Serial Nos. 562,556 and 562,557, filed November 8, 1944, and Serial No. 583,094, filed March 16, 1945, all assigned to the same assignee as the present application.

The ratio-measuring system also includes means responsive to variations in the other of said quantities, that is the fuel-mass flow to the device ill, for developing a second efiect of like type to the first effect varying with such other quantity. F'or example, this means may comprise a fuelmass flowmeter l6 connected in a fuel-intake conduit H to the device l and a second voltagedivider resistor [8 connected or otherwise coupled to the circuit II and including an adjustable contact element l8a actuated by the fuelmass flowmeter I6 for developing a second electrical signal varying in accordance with the fuelmass flow to the device l0. Likewise, if the fuelmass flowmeter i6 is of the power output type, it may be connected directly to actuate the adjustable contact l8a or, if it is not of the power output type, it may be coupled to the contact 18a through a torque amplifier l9, as shown. The fuel-mass fiowmeter l6 may also be of any suitable type such as the type described in the copending application of applicant and Frank G. Willey, Serial No. 562,558, filed November 8, 1944, and assigned to the same assignee as the present application.

The system of the invention also includes means for selecting an adjustable portion of one of the developed effects, which may be a third voltage-divider resistor 20 connected across the portion of the voltage divider M selected by its contact Ma and having an adjustable contact 20a for selecting an adjustable portion of the first signal. There are also provided means responsive to the difference between the selected portion of the first effect or signal developed at the adjustable contact 23a and the other of the developed effects appearing at the adjustable contact l8a for adjusting the selecting means to reduce this difference substantially to zero. This responsive means may comprise a comparison circuit 2! interconnecting the contacts 20a and lBa of the voltage dividers 2t] and i8, respectively, and including a comparing resistor 22 and means controlled by the comparison circuit for adjusting the contact 20a of the voltage divider 20 to balance the comparison circuit. This balancing means may comprise a polyphase reversible motor 23 connected to actuate the adjustable contact 20a and having a first phase Winding 23a connected across the supply circuit 3 l and having a second phase winding 23?) excited from the comparison circuit 2| through an amplifier and phaseshifter 24 having its input terminals connected across the resistor 22 and its output terminals connected to the phase winding 23b of the motor 23. The unit 24 is designed to apply to the phase winding 231) an alternating potential which is in quadrature with the potential applied to the phase winding 23a from the circuit H and leading or lagging in accordance with the sense of unbalance of the comparison circuit 26 to produce rotation of the motor 23 in a proper direction to rebalance the comparison circuit.

With the arrangement described, the adjustment of the selecting means, that is the contact 2011 of voltage divider 20, is representative of the ratio of the two quantities being measured, that is of the fuel-air ratio of the input to the combustion device Hi. Therefore, there may be provided ratio-indicating means such as an indicating scale 20b associated with the voltage divider 20 and a pointer element 200 which may constitute an extension of the adjustable contact 20a and is therefore adjustable in accordance with the adjustment of the selecting contact 20a.

Either or both of the air-mass fiowmeter i2 and the fuel-mass flowmeter it may have non-linear response characteristics or they may have dissimilar response characteristics, or both. In orv voltage divider 20 may be linear.

der to compensate for such non-linearities or dissimilarities, one or both of the voltage dividers l4 and I8 may be tapered or shaped to have a displacement-voltage characteristic proportioned to compensate for such non-llnearities or such dissimilarities, or both. Or, in case only one of the devices l2 and I6 has a non-linear characteristic and in case this characteristic is extremely non-linear, the compensation may be divided between the voltage-dividers i4 and I8 by properly tapering or shaping their displacement-voltage characteristics.

In general, the system also includes means for adjusting the air-mass flow to the device ill, represented schematically as a valve l3a in the conduit l3, and for adjusting the fuel-mass flow to the device l0, represented schematically as a valve Ila in the fuel-intake conduit l1.

It is believed that the operation of the ratiomeasuring system of the invention will be clear to those skilled in the art from the foregoing description. In brief, the voltage across the supply circuit may be represented by e1. The adjustable contact Ida actuated by the air-mass fiowmeter I2 then develops an electrical signal which may be represented by the voltage e2, varying with the air-mass flow to the device I0. Similarly, the voltage divider l8 develops at its contact No a voltage e3 varying in accordance with the fuel-mass flow to the device Ill. The adjustable contact 20a of voltage divider 20 selects an adjustable portion :24 of the signal oz. The difference between the voltages c4 and as is applied to the amplifier and phase shifter 24 which energizes the phase winding 23b of the motor 23 to actuate the motor in one direction or the other, dependin upon the polarity of the unbalance voltage in the comparison circuit 2| developed across the resistor 22. The motor 23 then operates to adjust the contact 20a of voltage divider 20 until the portion 84 of the voltage e2 at the contact Ma selected by the contact 20a is equal to the voltage as, at which time the input to the amplifier 24 is reduced to zero and the system is in equilibrium. In such equilibrium condition, the adjustment or position of the contact 20a is representative of, or a function of, the fuel-air ratio of the input to the device Ill. Therefore, by associating'with the voltage divider 20 the fuel-air ratio indicator scale 20b. suitably calibrated, the pointer 20c thereof will give a continuous measurement of the fuel-air ratio of the input to the combustion device I 0. It will be apparent that this measurement may be used to give either a visual indication, as shown, or may be utilized to operate a recording device or to effect a control of any desired operation, such as the operation of the valve I'Ia, to control the fuel-air ratio of the input to the device If the displacement-voltage characteristic of the voltage divider I4 is tapered or shaped to compensate for any non-linear response characteristic of the air-mass fiowmeter l2 and its associated torque amplifier 15, the electrical signal appearing at the contact Ha will be a linear function of the air-mass fiow to the device 10. Simi1ar1y,the electrical signal developed at the contact |8a of voltage divider l8 may be made a linear function of the fuel-mass flow to the device H). In such case, the displacement-voltage or displacement-resistance characteristic of the However, compensation for the non-linearities of response of the devices l2 and 5 may be distributed between the voltage dividers I4, I 8 and 20 in any desired manner provided the fuel-air ratio scale 20b is properly calibrated.

It is to be understood that the voltage dividers l4 and I8 have displacement-resistance characteristics and adjustment ranges properly related to the characteristics of the amplifiers I and I9, respectively, and to each other to permit a balance of the voltage 62, which is a fraction of the voltage e1, against the voltage e:, which is also a fraction of the voltage e1, under normal operating conditions.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

What is claimed as new is:

l. A system for continuously measuring the ratio of two variable quantities comprising, means for developing a first electrical signal varying with a first of said quantities, means for developing a second electrical signal varying with the other of said quantities, means for selecting an adjustable portion of one of said electrical signals, and means responsive to the difference between said portion of said one electrical signal and the other of said electrical signals for adjusting said selecting means to reduce said difference substantially to zero, the adjustment of said selecting means being representative of the ratio of said quantities.

2. A system for continuously measuring. the ratio of two variable quantities comprising, an electric supply circuit, a pair of voltage dividers coupled to said supply circuit each including an adjustable contact, means for adjusting the contact of one of said dividers in accordance with variations of a first of said quantities, means for adjusting the contact of the other of said dividers in accordance with variations of the other of said quantities, a third voltage divider connected across the portion of one of said pair of dividers selected by its contact, a comparing circuit including the contacts of said third divider and the other of said pair of dividers, and means controlled by said comparison circuit for adjusting the contact of said third divider to balance said comparison circuit, the adjustment of the contact of said third divider being representative of the ratio of said other quantity to said first quantity.

3. A system for continuously measuring the ratio of two variable quantities comprising, an alternating-current electric supply circuit, a pair of voltage dividers coupled to said supply circuit each including an adjustable contact, means for adjusting the contact of one of said dividers in accordance with variations of a first of said quantities, means for adjusting the contact of the other of said dividers in accordance with variations of the other of said quantities, a third voltage divider connected across the portion of one of said pair of dividers selected by its contact, a comparison circuit including the contacts of said third divider and the other of said pair of dividers, and a phase-sensitive device responsive jointly to the phase of the energization of said comparison circuit and that of said supply circuit for adjusting the contact of said third divider to balance said comparison circuit, the adjustment of the contact of said third divider being representative of the ratio of said other quantity to said first quantity.

4. A system for continuously measuring the ratio of two variable quantities comprising, an alternating-current electric supply circuit, a pair of voltage dividers coupled to said supply circuit each including an adjustable contact, means for adjusting the contact of one of said dividers in accordance with variations of a first of said quantities, means for adjusting the contact of the other of said dividers in accordance with variations of the other of said quantities, a third voltage divider connected across the portion of one of said pair of dividers selected by its contact, a comparison circuit including the contacts of said third divider and the other of said pair of dividers, and a polyphase reversible motor having a phase winding excited from said comparison circuit and operable in a direction dependent upon the sense of unbalance of said comparison circuit for adjusting the contact of said third divider to balance said comparison circuit, the adjustment of the contact of said third divider being representative of the ratio of said other quantity to said first quantity.

5. A system for continuously measuring the ratio of two variable quantities comprising, an electric supply circuit, a pair of voltage dividers coupled to said supply circuit each including an adjustable contact, means for adjusting the contact of one of said dividers in accordance with variations of a first of said quantities, means for adjusting the contact of the other of said dividers in accordance with variations of the other of said quantities, a third voltage divider connected across the portion of one of said pair of dividers selected by its contact, a comparison circuit including the contacts of said third divider and the other of said pair of dividers, means controlled by said comparison circuit for adjusting the contact of said third divider to balance said comparison circuit, and ratio-indicating means associated with said third divider and including a pointer adjusted in accordance with adjustment of the contact thereof.

6. A system for continuously measuring the ratio of two variable quantities comprising, an

electric supply circuit, a pair of voltage dividers coupled to said supply circuit each including an to compensate for dissimilarities in the response characteristics of said adjusting means, a third voltage divider connected across the portion of one of said pair of dividers selected by its contact, a comparison circuit including the contacts of said third divider and the other of said pair of dividers, and means controlled by said comparison circuit for adjusting the contact of said third divider to balance said comparison circuit, the adjustment of the contact of said third divider being representative of the ratio of said other quantity to said first quantity.

7. A system for continuously measuring the ratio of two variable quantities comprising, an electric supply circuit, a pair of voltage dividers coupled to said supply circuit each including an adjustable contact, means for adjusting the contact of one of said dividers in accordance with variations of a first of said quantities, means for adjusting the contact of the other of said dividers in accordance with variations of the other of said 7 quantities, each of said dividers having a displacement-voltage characteristic proportioned to compensate for any non-linearity in the response characteristic of its associated adjusting means, a third voltage divider connected across the portion of one of said pair of dividers selected by its contact, a comparing circuit including the contacts of said third divider and the other of said pair of dividers, and means controlled by said,

comparison circuit for adjusting the contact of said third divider to balance said comparison circuit, the adjustment of the contact of said third divider being representative of the ratio of said other quantity to said first quantity.

DAVID W. JR.

REFERENCES CITED I file of this patent:

Number Number UNITED STATES PATENTS Name Date Gibson Nov. 30, 1915 Midyette Apr. 18, 1939 Bond July 23, 1940 Luhrs Oct. 8, 1940 Rosecky Feb. 18, 1941 Jones Oct. 28, 1941 Luhrs June 16, 1942 Harrison Nov. ;3, 1942 Harrison Apr. 13, 1943 Bristol May 25, 1943 Luhrs Feb. '22, 1944 Lilja. et a1. Sept. 19, 1944 FOREIGN PATENTS Country Date Great Britain July 10, 1935 Great Britain June 11, 1943 

